CARROLL COUNTY

Carroll County lies entirely in the Piedmont province. It is divided. into two nearly equal parts by Parr's Ridge which runs in a northeastsouthwest direction from Wentz to Mount Airy. This ridge, capped with igneous rocks known as phyllites, reaches an elevation of about 800 feet at the southern border of the county, rising to over 1000 feet at its northern boundary. This ridge forms the dividing line between the streams flowing directly into Chesapeake Bay and those tributary to the Potomac River. The eastern portion of the county is a much dissected rolling upland with narrow stream valleys, the hills ranging from 500 to 800 feet in height. West of Parr's Ridge the surface becomes gradually less in elevation to about 400 feet in the Monocacy Valley at the western border of the county.

Below the surface soil and mantle of weathered rock the county is, with the exception of the western portion to the north and west of Union Bridge, underlain by a complex of crumpled and faulted crystalline rocks of igneous and metamorphic origin. There is some granite around Sykesville and phyllites at Finksburg, but with this exception the eastern quarter of the county is underlain by Wissahickon gneiss, giving rise to loamy micaceous soils and hence good farming land. Aside from small

patches of diabase, marble, and gneiss, the central portion of the county consists of a complex of acid and basic volcanic rocks, giving rise to heavy soils in the valleys and rocky, thin soils on the ridges, which are nevertheless good farming lands. Underlying the western third of the county are the red and gray sandstones and shales of the Newark formation—sedimentary deposits of Triassic age which furnish what are chiefly grass and wheat lands.

SURFACE WATERS

Carroll is well supplied with small streams furnishing very many small water powers for local milling operations. The larger streams include the Gunpowder which crosses the northeastern corner of the county, the Monocacy which forms the boundary of the county on the west, and the two branches of the Patapsco along the eastern and southern boundaries. Since the population is largely agricultural there has been no demand for the utilization of stream water with its risks of fluctuating supply and contamination. The municipalities have hitherto utilized the abundant springs or have driven wells for their supplies.

UNDERGROUND WATERS

Artesian Waters

Aside from the purposes of municipal supplies the need for artesian water has not been acutely felt throughout the county and while a considerable number of shallow wells have been drilled there are few deep wells in the county. The nature of the underlying rock throughout most of the county in which the water is confined to joint and fault planes renders it impossible to forecast artesian prospects with any degree of confidence, such as is possible outside the Piedmont belt where the various geological formations are in undisputed succession and contain many permeable beds at definite horizons. Since 1903 the Union Bridge Water Company has put down six wells. These are all 6 inches in diameter and range in depth from 50 to 464 feet. The water is probably obtained from the sandstone beds of the Newark formation of Triassic age and is slightly hard. The water in all the wells heads about 12 feet below the surface. The two 50-foot wells pump 50 gallons, as does another 246 feet deep. A